Automatic air feed pressure control for rock drills



Feb. 8, 1955 s. D. GUNNING ETAL AUTOMATIC AIR FEED PRESSURE CONTROL FOR ROCK DRILLS Filed Feb. 20, 1952 4 Sheets-Sheet 1 I I'Illlliflllillllllil INVENTORS. SAMUEL D.GUNN|NG JACOB E. FEUCHT ATTORNEY Feb. 8, 1955 s. D. GUNNING ET AL AUTOMATIC AIR FEED PRESSURE CONTROL FOR ROCK DRILLS 4 Sheets-Sheet 2 Fiied Feb. 20, 1952 5 RG (T WW a tqi NW W Um" 4 E x D. N j E m mm M I mm I] aw T fiv vvvy mm M w I ll say 1 I w B M61 m kw 9. 2. mm v t. m 9. E. Q. 2. w m

55 s. D. GUNNING ETAL AUTOMATIC AIR FEED PRESSURE CONTROL FOR ROCK DRILLS 4 Sheets-Sheet 3 Filed Feb. 20, 1952 w OI Q mm 5 E W 7/4 mm m wm/ mm 5 H mm mm mwX V \r/ mnr mm mm H B E 2% on -m vm mm mm mm mm H mm 1 a 5 mm m? 5 mm 9 mv mv mm s R Q MMT NIH ENC VNU N E IGF 5 mm mm s N 5 mm L m EB T. Ww r n MM A mm mm M mm h on on ET n? mm mm @m H A 5 mm 3 m 1955 s. D. GUNNING ETAL 2,701,551

AUTOMATIC AIR FEED PRESSURE CONTROL. FOR ROCK DRILLS Filed Feb. 20, 1952 4 Sheets-Sheet 4 FIG? FIG. 8

47 46 INVENTORS.

SAMUEL D. GUN G B ACOB E. FEUC 6 ATTORNEY United States Patent AUTOMATIC AIR FEED PRESSURE CONTROL FOR ROCK DRlLLS Samuel D. Gunning, Cleveland Heights, and Jacob E. Feucht, Garfield Heights, Ohio, assignors, by mesne assignments, to Westinghouse Air Brake Company, a corporation of Pennsylvania Application February 20, 1952, Serial No. 272,592 Claims. (Cl. 1219) This invention relates broadly to fluid actuated rock drills, but more particularly to the feeding mechanism for rock drills of the stoper type.

One object of this invention is to produce a stoper drill having a plurality of telescopically mounted fluid actuated feeding or lifting cylinders, with a simple and eflicient pressure controlling device enabling said elements to deliver a uniform lifting force irrespective of their different sizes.

Another object of this invention is to produce such stoper drill with adequate valve mechanism assuring complete extension of one of its feeding elements prior to the extension of the other.

Another object of this invention is to produce an improved stoper type rock drill forming a compact assembly, which is strong, durable and efiicent.

Other objects of this invention will be apparent from the following detailed description wherein similar characters of reference designate corresponding parts and wherein:

Figure 1 is a longitudinal sectional view of the stoper drill embodying the invention and showing the feed mechanism in completely retracted position.

Figure 2 is an enlarged longitudinal sectional view of the feed mechanism shown in partly extended position, while Figure 3 is a similar view in fully extended position.

Figures 4, 5 and 6 are enlarged longitudinal sectional views of the upper end of the feed mechanism showing parts in different positions.

Figures 7 and 8 are enlarged longitudinal sectional views of the lower end of the drilling motor in Figure 1, showing the throttle valve in different positions, and

Figure 9 is an enlarged cross sectional view taken substantially on line 9-9 in Figure 3, and looking in the direction of the arrows.

Referring to the drawings, 10 designates the usual fluid actuated rock drill of the percussive type, which may briefly be described as including a cylinder 11 having a piston 12 reciprocable therein with a stem 13 adapted to deliver impacts to the shank 14 of a drill steel 15. Drill steel shank 14 is slidably mounted in a chuck 16 journalled in a front housing 17 which is rigidly secured to cylinder 11 by side bolts, not shown.

In the lower end of cylinder 11, there is provided the usual fluid distributing mechanism which may include a valve chest 18 having a valve 19 slidable therein for automatically controlling ports and passages through which motive fluid is alternately admitted in the ends of the cylinder 11 for eflecting reciprocation of piston 12. Forming the lower end of the rock drill, there is a back head 20 equipped with a rotatable throttle valve 21, and a feed mechanism supporting bracket 22, both back head and bracket being rigidly secured to cylinder 11 by side bolts, not shown.

The feed mechanism, generally designated by 23, includes a substantially vertical cylindrical housing 24 having its lower end rigidly secured to the bracket 22 and its upper end to a similar bracket 25 which extends laterally from the front housing 17. In this manner the outer cylinder 24 is rigidly secured to the rock drill 10 in parallel alignment therewith.

The upper end of housing 24 is closed by a disk or head 26 held between two spilt spring clips 27 and carrying two ring packings 28 assuring a fluid tight joint of the head with the housing. Head 26 is formed with a central bore 29 having closely fitted therein the upper reduced end 2,701,551 Patented Feb. 8, 1955 of a central inner tube 30 which depends therefrom. This tube has an annular shoulder 31 engaging one side of the head, while the other side is engaged by a gland nut 32 which rigidly secures the tube to the head and closes its upper end. Immediately below the gland nut 32, there is formed in the tube 30 a valve chamber 33 having fitted therein a stationary valve seat member 34 of a diameter smaller than that of the valve chamber. The valve seat has a central bore 35 of a diameter substantially larger than that of a stem 36 slidable therethrough and having an integral valve head 37 engageable with one side of seat 34 for closing bore 35. A compression spring 38 is interposed between the other side of seat 34 and a washer 39 retained on the free end of valve stem 36 by a split spring clip 40, thereby causing valve 37 to be spring pressed into engagement with its seat.

The throttle valve 21, rotatable within the rock drill back head 20, has a pressure fluid conveying bore 41 connected to a moon like groove 42 through a radial port 43. Diametrically opposed to groove 42, the throttle valve is formed with another similar groove 44 which is in constant registration with an exhaust port 45. From inlet groove 42, pressure fluid may be admitted through a port 81 into an inlet chamber 46 formed between back head 20 and bracket 22 and sealed by a packing 47. Closely fitted in the bracket 22, there is one end of a fluid conveying conduit 48 having its other end closely fitted in a connector 49 welded to the upper end of the feed cylinder 24. From inlet chamber 46 pressure fluid is free to flow to conduit 48 through bracket port 50 and in an annular groove 51 provided in the cylinder head 26 between packings 28 through connector port 52. From annular groove 51 it may flow into central tube 30 below valve seat 34 through a passage 53, and from the valve chamber 33 into feed cylinder 24 below its head 26 through a port 54, which port together with the valve chamber 33 and valve seat bore 35 form a passage-way controlled by the spring pressed valve 37.

Extending longitudinally through the cylinder head 26, there is a bore 55 closed at one end by a plug 56 while the other end opens into the cylinder 24. This bore or by-pass communicates with annular groove 51 through a port 57, and may be closed by an exhaust valve 58 engageable with an annular seat 59 formed intermediate the ends of the bore. When valve 58 is closed, that is engaging seat 59, it partly uncovers port 57 to enable admission of pressure fluid on the valve from annular groove The lower end of the inner tube 30 is internally threaded to receive a stud 60 having a central through port 61. Clamped between the end of tube 30 and the small head of the stud, there is a washer 62 which is somewhat larger than the tube and a split spring collar 63. The lower end of the cylindrical housing 24 is reinforced by an annular bead 64, preferably welded thereto, and having mounted therein a guide bushing 65 which is axially retained between the end of cylinder 24 and a split spring clip 66 carried by head 64.

Slidably mounted in the housing 24, there is a piston head 67 carrying packings 68 and 69 affording fluid tight JOlDlS with the housing and the inner tube 30 respectively. Piston head 67 has a threaded shank 70 having screwed thereon a packing follower 71, which also has a threaded shank 72 having screwed thereon the upper end of a main cylinder 73. The downward movement of piston 67 and its attached cylinder 73 is limited by engagement of piston shank 70 with washer 62 carried by the lower end of inner tube 30. Main cylinder 73 is substantially smaller than the interior of housing 24, and is slidably guided therein and through the lower end thereof in the bushing 65. The lower end of main cylinder 73 has a bushing 74, retained therein by split spring clips 75, through which is slidably guided a secondary cylinder 76. The inner end of this last cylinder is formed with a piston head 77 which carries the usual packing 78, While its outer end is equ'pped with a pointed anchor 79 which remains outside of housing 24 and main cylinder 73 even when the feeding mechanism is entirely retracted as shown in Figure 1. In order to prevent accidental extension of the feed mechanism when the rock drill is being carried about, the anchor 79 is provided with a bore 80 with the wall of which the split spring collar 63 carried by the lower end of tube 30 is capable of frictional locking engagement.

In the operation of the tool, motive fluid controlled either by the throttle valve 21 or by another secondary valve, not shown, is delivered to the rock drill 10 to effect reciprocation of its piston 12 in the usual manner. When the throttle valve is positioned as shown in Figure 7, motive fluid from the valve bore 41 is supplied to the inlet chamber 46 via valve port 43, groove 42 and port 81. From inlet chamber 46 it is free to flow into annular groove 51 of the housing head 26 via port 50, conduit 48 and connector port 52. If the feed mechanism is fully retracted as shown in Figure 1, motive fluid from annular groove 51 will flow in tube 30 through passage 53 and into the secondary cylinder 76 through stud port 61, and therefrom into the main cylinder 73 to act on the effective actuating area of the secondary cylinder and effect extension of said last cylinder through the open end of cylinder 73. As clearly shown in the drawings, the effective actuating area of secondary cylinder 76 is equal to the inner cross sectional area of the main cylinder 73. In this instance, motive fluid from annular groove 51 is also admitted on the exhaust valve 58 through the partly uncovered port 57 to maintain the valve closed, while valve 37 is spring closed, that is, closed by the compression spring 35. fluid in tube 30 is expanded to effect the extension of the secondary cylinder 76, its pressure is lower than thereafter when the secondary cylinder has been fully extended and its piston 77 engages the bushing 74. During this low pressure in tube 30, the spring 38 maintains valve 37 closed relative to passage-way 35-54. As pressure in tube 30 increases after the extension of secondary cylinder 76, it will act on the exposed end or actuating area of the valve to overcome the spring 38 and shift the valve open relative to said passage-way. With valve 37 opened, its upper end engages gland nut 32, while its lower end or actuating area remains subjected to the action of the high pressure in tube 30 to keep valve opened and admit motive fluid from tube 30 through passage-way 3554 into the upper end of housing 24 to act on piston 67, that is on the effective area of the main cylinder 73 and cause its extension through the open end or guide bushing 65 of housing 24. In this instance, the secondary cylinder 76 remains extended relative to the main cylinder 73 by the action of the motive fluid still admitted in the secondary cylinder, thereby causing it to move in unison with the main cylinder 73. In practice, the capacity of the passage 53 is somewhat greater than that of the passage-way 35-54, thereby assuring the motive fluid pressure acting on the actuating area of the secondary cylinder 76 to be greater than that acting on the actuating area of main cylinder 73. The difference in the sizes of passage 53 and passage-way 3554 is calculated to produce a pressure differential on the actuating areas of the cylinders 73, 76 causing the lifting or extension forces of both cylinders to be substantially equal.

The extension of the main cylinder 73 relative to housing 24 is limited by engagement of its piston 67 with the washer 62 carried by the lower end of tube 30.

When it is desired to retract or collapse the feed mechanism, the throttle valve 21 may be positioned as shown in Figure 8, thereby shutting off supply of motive fluid to port 81 and effecting communication of this port with the exhaust port 45 through the valve exhaust groove 44. Motive fluid in the tube 30 is now free to exhaust therefrom through the same ports and conduits which previously admitted it therein, thereby reducing the pressure in the cylinders 73, 76 and causing secondary cylinder 76 to retract into the cylinder 73 by virtue of the weight of the entire drilling tool thereon. As the pressure of the fluid in tube 30 is reduced, the spring 38 will again close the valve 36, preventing exhaust of motive fluid from housing 24 through passage-way 35-54. However, since the annular groove 51 is also exhausted, motive fluid pressure therein previously maintaining exhaust valve 58 closed, is now sufficiently reduced to enable opening of the valve by motive fluid trapped in housing 24, thereby enabling free exhaust from housing 24 through bypass 55, port 57 and annular groove 51 and retraction of cylinders 73 and 76 into housing 24 by virtue of the weight of the entire drilling tool thereon.

From the foregoing description, it will be understood As the motive' that by providing the spring-pressed valve 37 to enable admission of motive fluid into housing 24 only when motive fluid pressure in tube 30 has reached a predetermined maximum, the smallest of the telescoping cylinders is always first to extend from its retracted position. Its extension continues until it reaches the end of its extension stroke. Thereafter increased pressure in the tube 30 causes valve 37 to open to effect extension of the largest telescoping cylinder. Since the fluid conveying capacity of the passage-way leading to the cylinder having the largest actuating area is smaller than that of the passage leading to the cylinder having the smallest actuating area, the pressure per square inch on the largest area is smaller than that on the smallest area to an extent calculated to cause the feeding motions imparted to the rock drill to be of uniform or equal force.

I claim:

1. A fluid actuated feeding mechanism including a substantially vertical cylindrical housing having a closed upper and an opened lower end, main and secondary cylinders telescoping in said housing each having a piston fixed to the inner end thereof, a tube having its upper end fixed to the closed end of said housing extending through the piston of and into said main cylinder, a passage opening in the upper end portion of said tube supplying motive fluid thereinto to be discharged into said main cylinder for effecting extension of said secondary cylinder, means adjacent the outer end of said main cylinder engageable by the piston of the secondary cylinder for limiting outward movement of the secondary relative to the main cylinder, the motive fluid pressure in said tube being lower during and by virtue of said extension and higher thereafter, a passage-way capable of supplying motive fluid from said tube into said housing to effect extension of said main cylinder, means on the lower end of said tube engageable with the piston of the main cylinder for limiting outward movement of the main cylinder relative to said housing, a valve seat in said tube above the opening of said passage, a spring pressed valve operatively engaging said seat for closing said passage-way during said lower pressure, and an actuating area on said valve responsive to said higher pressure for shifting said valve from said seat and opening said passage-way.

2. A feeding mechanism including a cylindrical housing having a closed and an opened end, main and secondary piston headed fluid actuated cylinders telescoping in said housing, an effective actuating area for each of said cylinders greater for the main than for the secondary, a tube having one end fixed to the closed end of said housing and the other end opening into said cylinders below the piston head of the main one, a passage supplying motive fluid into said tube to be discharged into said cylinders to effect extension of the secondary one, the motive fluid pressure in said tube being lower during and by virtue of said extension and higher immediately thereafter, a passage-way capable of supplying motive fluid from said tube into said housing above the piston head of said main cylinder to effect its extension, a spring pressed valve controlling said passage-way subjected to the motive fluid pressure in said tube, said valve being spring closed against said lower and opened by said higher pressure, the motive fluid supplying capacity of said passage-way and consequently the motive fluid pressure actuating said main cylinder being smaller than the capacity of said passage and the motive fluid pressure actuating said secondary cylinder to an extent causing the extension forces of both cylinders to be substantially equal, and means including an exhaust valve controlled by-pass through which motive fluid trapped in said housing above the piston head of said main cylinder after the closing of said passageway is free to exhaust therefrom to enable retraction of said main cylinder, said exhaust valve being normally closed by the pressure of the motive fluid admitted in said tube and opened by the pressure of said trapped motive fluid.

3. A feeding mechanism including a substantially vertical cylindrical housing having a closed upper and an opened lower end, a piston slidable in said housing having a main cylinder fixed thereto and slidable through said opened end, said cylinder having a lower opened terminal, a piston head slidable in said main cylinder having a secondary cylinder fixed thereto and slidable through said opened terminal, an effective actuating area for each of said cylinders greater for the main than for the secondary,

a tube extending through said piston having its upper end fixed to the closed end of said housing and its lower end opening into said main cylinder, means on the lower end of said tube engageable by said piston for limiting outward movement of said main cylinder relative to said housing, means adjacent said open terminal engageable by said piston head for limiting outward movement of said secondary relative to said main cylinder, a passage opening in the upper end portion of said tube supplying motive fluid thereinto to be discharged into said main cylinder below said piston for effecting said outward movement of said secondary cylinder, the motive fluid pressure in said tube being lower during and higher immediately after outward movement of said secondary cylinder, a passage-way capable of supplying motive fluid from the upper end portion of said tube into said housing above said piston for effecting said outward movement of said main cylinder, a valve seat in said tube above the opening of said passage, and a spring pressed valve operatively engaging said seat for closing said passage-way during said lower pressure and shifted by said higher pressure from said seat for opening said passage-way, said passage-way being of a size calculated to supply less motive fluid to said main cylinder than that supplied to said secondary cylinder through said passage and tube, thereby resulting in the outward movement of both cylinders to be substantially of equal force.

4. A fluid actuated feeding mechanism including a cylindrical housing having a closed and an opened end, main and secondary cylinders telescoping in said housing, sealing means between the interiors of said housing and main cylinder, a motive fluid conveying tube depending from the closed end of said housing into said main cylinder to supply motive fluid thereinto effecting extension of said secondary cylinder, the motive fluid pressure in said tube being lower during by virtue of said extension and higher thereafter, a passage-way capable of supplying motive fluid from said tube into said housing to effect extension of said main cylinder, means enabling said tube to be selectively connected to a source of motive fluid or to an exhaust port, the pressure of the motive fluid in said tube being lower during and by virtue of its exhaust therefrom, a spring pressed valve controlling said passageway subjected to the motive fluid pressure in said tube, said valve being spring closed during said lower pressure, an actuating area on said valve responsive to said higher pressure for opening the valve, and means automatically by-passing said closed passage-way when motive fluid is exhausting from said tube to enable exhaust from said housing irrespective of said sealing means.

5. A fluid actuated feeding mechanism including a cylindrical housing having a closed and an open end, main and secondary cylinders telescoping in said housing, an actuating area for each of said cylinders, a tube depending from the closed end of said housing into said main cylinder, means for admitting or exhausting motive fluid in and from said tube and the actuating area of said secondary cylinder to effect its extension or enable its retraction relative to said main cylinder, a passage-way leading from said tube into said housing for admitting motive fluid therethrough to the actuating area of said main cylinder to effect its extension relative to said housing, means including a valve automatically closing said passage-way upon exhaust of motive fluid through said tube, and means including an exhaust valve controlled by-pass through which motive fluid trapped on the actuating area of said main cylinder after the closing of said passage-way is free to exhaust therefrom to enable retraction of said main cylinder, said exhaust valve being normally closed by the pressure of the motive fluid admitted in said tube and opened by the pressure of said trapped motive fluid.

References Cited in the file of this patent UNITED STATES PATENTS 902,723 Gauer Nov. 3, 1908 2,134,859 Collins Nov. 1, 1938 2,208,025 Feucht July 16, 1940 2,438,285 Houldsworth Mar. 23, 1948 

